In many technological processes the cleaning and/or grading machines for free-flowing materials ensure the production of a semi-finished or finished product of the required quality. For example, the modern agriculture methods cannot be practically provided without the use of such machines. Known in the prior art are many types of separating machines which differ from one another mainly by the methods used for separating free-flowing materials into fractions. Of all the types of separating machines used in agriculture the most common ones are the air-and-screen separating machines which separate the free-flowing materials by airblast and screens. In the first place these machines clean the seeds of many types of impurities and grade them in order to select the ones most likely to germinate. Therefore, improvement of the known designs of such machines and creation of radically new ones constitutes a vital technical problem.
Widely known in the prior art are cleaning and/or grading machines for free-flowing materials which comprise a frame on which are mounted one or two vertical air channels with aspirating chambers, a system of flat screens, a drive for vibrating the screens, and screen cleaning devices. In most cases such machines ensure the requisite quality of cleaning and/or grading of free-flowing materials but their output in relation to their size is comparatively low. This should be attributed to the fact that the intensity of separation in these machines is governed mainly by the effect of gravity forces which have a certain value for each kind of mixture of free-flowing materials. Therefore, acceleration of the particles of a free-flowing material during separation does not exceed 9.81 m/s.sup.2 which limits the intensity of separation.
Known in the prior art is a cleaning and/or grading machine for free-flowing materials, including grain and seeds (see, for example U.S. Pat. No. 3,794,166. Cl. USA 209/301). This machine comprises a housing with a movably mounted screen made in the form of a body of revolution, a drive which imparts a rotary motion and vertical vibration to the screen, a screen cleaner in the form of a body of revolution installed at one side of the screen and pressed by springs against its external surface. Such a machine gives a considerable gain in the output referred to its mass due to the utilization of the centrifugal forces of inertia of the particles of free-flowing materials for intensifying the process of separation. However, this machine can incorporate only one screen and thus can separate the free-flowing material only into two fractions; the machine has no air separating channel which prevents the free-flowing material from being cleaned and/or graded by the weight of the particles. Inasmuch as the screen cleaner is installed at only one side of the screen, this falls to ensure the required intensity of cleaning of the screen holes because after the screen has turned through an angle equal to approximately .pi. radians, these holes are again heavily clogged with the particles of the separated material which cuts down sharply the output and performance of the machine. The use of only one type of hole cleaner with a smooth surface also reduces considerably the efficiency of the machine because a sizable proportion of the particles of the free-flowing material cannot be forced out of the holes by the cleaner of one type alone. These disadvantages reduce substantially the efficiency of such a machine in, say, agriculture.
There are also other known cleaning and/or grading machines for free-flowing materials (see, for example, Author's Certificate USSR No. 506439, Int. Cl. BO7 B 1/44). This machine comprises several identical air-and-screen separating units rigidly secured on the frame, a drive for actuating the working elements of the units, and aspirating chambers connected with said units. Each unit consists of a hollow housing accommodating a consecutively arranged air-separating device and a vertical rotor. Mounted movably on the rotor is a screen drum with several consecutively arranged screens made in the form of a body of revolution. Installed on the upper part of the rotor, coaxially therewith, on bearings is a thrower in the form of a truncated cone with a smooth surface, drive, by the rotor via a reduction unit. The screen drum and screens are of the inseparable construction, the screens being rigidly secured on the drum. At one side of the screen drum are installed screen cleaners made in the form of a body of revolution and provided with a bristly surface. The cleaners are articulated to the unit housing and pressed against the external surface of the screens. For receiving the free-flowing material each unit incorporates a batching device constituted by a cylindrical pipe with a gate installed thereon. The screens are put in vibratory motion by crank-type vibrators rigidly secured to the frame of the machine. The screen drum with screens rotates around a vertical axis and simultaneously vibrates along the same axis.
The free-flowing material delivered into the machine is first treated with air for separating the "light" particles then consecutively by several screens for separating the material into the required number of fractions. Due to the effect of the centrifugal forces of inertia on the particles of the material being separated by the rotating and vibrating screens the output and performance of the latter are radically improved. The amount of the material loaded into the machine can be controlled by changing the height of the gap between the gate and the thrower bottom.
This machine is favourably distinguished from the other prior art machines by high output and versatility, for example, by the possibility of separating the material into more than two fractions and grading it by the weight of particles. However, this machine has substantial disadvantages too. The fact that the screen drum and screens are inseparable and that the screens are rigidly secured on the drum complicates considerably the replacement of screens in case of their wear or when shifting over to treatment of another kind of free-flowing material and reduces substantially the standardization of machines which incorporate screen drums with a different number of screens. The use of only one type of cleaners, e.g. with a bristly surface and installed only at one side of the screen drum constitutes the same disadvantage as that of the other machines. The provision in the machine of the reduction unit for driving the thrower complicates the design and impairs reliability. The batching device in the form of a cylindrical pipe with a gate installed thereon fails to ensure the requisite uniformity of batching of the free-flowing material thus reducing the efficiency of the machine. All these factors taken together complicate the employment of the machine and reduce the degree of standardization of such machines characterized by different output and application.
The main object of the present invention resides in a considerable increase in the efficiency of separation of free-flowing materials.
Another object of the present invention resides in stepping up the degree of standardization of the cleaning and/or grading machines for free-flowing materials of different output and application.
Still another object of the present invention resides in simplifying substantially the replacement of screens in service.
An important object of the present invention resides in simplifying the design of the cleaning and/or grading machine for free-flowing materials.
Another important object of the present invension resides is providing a cleaning and/or grading machine for free-flowing materials wherein a modification of the design of the screen drum, screens, screen hole cleaners, batching device and thrower would increase considerably the efficiency of the machine and simplify its design and operation.